Coupling tooth of a selector sleeve of a gear coupling for coupling a gear wheel to its shaft

ABSTRACT

To guide it in the circumferential directions, a clutch tooth of a selector sleeve of a gear wheel clutch for coupling a gear wheel to its shaft has two central guide faces and additional guide faces on its ends.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a particularly configured clutch toothof a selector sleeve.

According to European publication EP 0 288 718 B1, all the clutch teethof a selector sleeve of a gear wheel clutch for coupling a gear wheel toits shaft can be configured either in accordance with the generic typeor symmetrically to the significant longitudinal center plane of thetooth in such a way that the respective reduced tooth flank portion isin the form of a recess in the side flank of the tooth. A correspondingundercut tooth flank portion of a clutch tooth of the gear wheel engagesinto this recess with radial overlap in the engaged state in order toprevent the selector sleeve from jumping back into its neutral position.

In known selector sleeve clutch teeth of the generic type in Europeanpublication EP 0 276 382 B1 and German Patent 845,903, the respectivelyreduced tooth flank portions are in the form of recesses in the sideflanks of the tooth. In the case of the European publication, theserecesses interact with undercut tooth flank portions and, in the case ofthe German patent, they interact with recesses in the side flanks of theclutch teeth of the gear wheel to prevent the selector sleeve fromjumping out of the clutch toothing of the gear wheel. In these knownclutch teeth with reduced tooth flank portions in the form of recessesin the side flanks of the tooth, the oblique end faces at the ends doadmittedly merge into the respective recess by way of additional guidefaces extending parallel to the significant longitudinal plane of thetooth, thus advantageously increasing the guiding length of the selectorsleeve. In these known selector-sleeve clutch teeth, however, there isan unwanted increase in the engagement travel of the gear wheel clutchbecause the tooth portion extending axially between the recess and theend of the tooth requires an idle travel as spacing with respect to thegear wheel.

European publication EP 0 195 706 B1 discloses a selector sleeve of agear wheel clutch for coupling a gear wheel to its shaft withnon-generic clutch teeth without undercut tooth flank portions. In theclutch, the two mutually opposite flanks of each pair or the majority ofpairs of successive clutch teeth alternately have two central thickenedportions, between which one of the driver teeth associated in a mannerfixed in terms of motion to the shaft engages in a displaceable manner,or two projections provided on the ends and extending out in thecircumferential direction, the projections each entering into radialoverlap, when the selector sleeve is moved into its coupled position,with an undercut tooth flank portion of a clutch tooth of the gear wheelin order to prevent the selector sleeve from jumping back into itsneutral position. Apart from the fact that the projections of the clutchteeth of the selector sleeve have an unfavorable effect when passingthrough the locking toothing of the synchronizer ring, those clutchteeth in this known selector sleeve, which do not have central thickenedportions but are only provided with the end projections, cannot exercisea guiding function, and the torque transmission capacity of the selectorsleeve is thus impaired.

German publication DE 44 13 169 C1 discloses a clutch tooth of aselector sleeve of a gear wheel clutch for coupling a gear wheel to itsshaft. The guide portion, which is arranged centrally in relation to thedirections of the center line of the selector sleeve, is bounded in bothperipheral directions of the center line by a respective guide faceextending parallel to the center line. The guide portion can beintroduced, so as to be axially displaceable and fixed in terms ofrotation, into an axial driver toothing concentric with and fixed interms of movement relative to the shaft. Each of the ends forming aboundary in the directions of the center line has two oblique end faces,which are arranged in a roof shape relative to one another, the commonvertex edge of which lies in a significant longitudinal plane of thetooth containing the center line. The side flanks each comprise oneguide face of the guide portion, a tooth flank portion which adjoins itin the direction of the center line towards one end and is at a reduceddistance from the significant longitudinal plane of the tooth, and theoblique end face, which, like the guide face, lies on the same side ofthe significant longitudinal plane of the tooth and in which one obliqueend face merges directly into an undercut tooth flank portion. In thedirection of the guide portion, the undercut tooth flank converges withstraight flank lines relative to the significant longitudinal plane ofthe tooth. The other oblique end face merges, in the direction of thecenter line towards the guide portion, into an overall guide surfacewhich extends parallel to the center line and forms a continuouscoherent surface with the guide-portion guide face on the same side ofthe significant longitudinal plane of the tooth and the distance ofwhich from the significant longitudinal plane of the tooth is less thanthe distance of the guide-portion guide face on the other side of thesignificant longitudinal plane of the tooth from the significantlongitudinal plane of the tooth.

The object on which the invention is based is essentially to avoidincreasing the engagement travel (gear-change travel) as described whileretaining an increased guiding length.

In the clutch tooth according to the invention, a third guide face isformed on one flank side in the region of one end. This guide facesignificantly extends the guiding length of the clutch tooth in thecoupled position of the selector sleeve, with the result that theselector sleeve no longer sticks in the driver toothing associated withthe shaft.

The clutch tooth according to the invention, in the initial state, issymmetrical with undercut tooth flank portions on both tooth flank sideson both sides of a longitudinal center plane of the tooth. The clutchtooth can be produced from a conventional clutch tooth by reducing thethickness of the tooth by a constant amount parallel to the center lineof the selector sleeve, on one side of the originally centrallongitudinal plane of the tooth, to such an extent that a relativelyshort, separate, third guide face is formed on the end concerned.

An advantageous feature of the invention is that, the selector sleevecan be provided both with conventional clutch teeth with symmetricalundercut tooth flank portions and with clutch teeth according to theinvention, with a third guide face in the region of the ends.

An additional advantageous feature of the invention is that the clutchteeth can be divided into two groups which initially, starting from acommon initial tooth thickness, are all symmetrical and have the samedimensional shape and depth of the undercut tooth flank portions.

A first group of teeth comprises conventional symmetrical teeth whichact in the customary manner as regards all the functions of toothingsuch as meshing, locking, releasing, idle travel and gear retention.

The thickness of the teeth of a second group is reduced on one sideduring the manufacturing process. The driver toothing associated withthe shaft is thickened at the corresponding points by the amount removedfrom the selector sleeve, and the backlash thus remains unaltered.During the production of such a selector sleeve, the selector sleeve isinitially symmetrical, i.e. has been broached with a group of initialteeth and rolled to give a uniform shape to the undercut tooth flankportions. In the subsequent operation, namely calibration broaching,both the small calibration amount and also, in addition, the tooththickness are removed from the guide faces with a correspondinglydesigned broach to give the third guide face. This method isadvantageous because, in contrast to conventional toothing, neitheradditional operations nor rolling of undercut tooth flank portions ofdifferent depths is required.

In gear wheel clutches for coupling a gear wheel to its shaft, it iscustomary to use an annular selector sleeve carrier which is arrangedconcentrically and fixed in terms of motion relative to the shaft, andwhich carries the driver toothing for the selector sleeve. Applying theinvention to a gear wheel clutch of this kind, the selector sleeve andthe driver toothing in this clutch can be configured in order to givesymmetrical tooth gaps on the selector sleeve with in each case twoasymmetrical clutch teeth lying symmetrically to the thickened drivertooth of the selector sleeve carrier. The advantage of a gear wheelclutch configured in this way lies in the simple configuration of theselector sleeve carrier obtained from external suppliers, which can thusbe fitted as it arrives.

The invention is described in greater detail below with reference to anembodiment illustrated schematically in the drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an axial section through a gear wheel clutch for coupling agear wheel to its shaft, with a selector sleeve having clutch teeth inaccordance with the invention,

FIG. 2 shows a longitudinal section in the form of a development throughthe toothing of the selector sleeve and the selector sleeve carrier ofthe gear wheel clutch of FIG. 1,

FIG. 3 shows a longitudinal section through one of the clutch teeth,according to the invention, of the selector sleeve in FIG. 1,

FIG. 4 shows the detail IV of the clutch tooth in FIG. 3 on an enlargedscale,

FIG. 5 shows a longitudinal section in the form of a development throughthe gear wheel clutch in FIG. 1 in the coupled state of the selectorsleeve and on an enlarged scale; in FIG. 5, only the engagement withradial overlap of the undercut tooth flank portions of one of theconventional clutch teeth of the selector sleeve and of a clutch toothof the gear wheel to be coupled are shown, and

FIG. 6 shows a longitudinal section in the form of a developmentcorresponding to the illustration in FIG. 5 through a gear wheel clutchin which the clutch teeth of the selector sleeve are configured in amanner different from the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Arranged concentrically and in a manner fixed in terms of motion on ashaft which is coaxial to a center line 14—14 of a gear wheel clutch 11but is not shown specifically is an annular selector sleeve carrier 13.On its outer circumference, the carrier has outer axial driver toothing18 into which a likewise annular selector sleeve 10 arrangedconcentrically with the center line 14—14 engages in an axiallydisplaceable and rotationally fixed manner by way of corresponding innerclutch toothing 7, 8.

Mounted rotatably and in an axially non-displaceable manner on theshaft, laterally adjacent to the selector sleeve carrier 13, is a gearwheel 12 which, on its end facing the selector sleeve carrier 13, has aclutch ring 44 which is concentric with the center line 14—14, isarranged so as to be fixed in terms of motion relative to the gear wheel12, and has outer clutch toothing 45 into which the selector sleeve 10can be moved axially by means of its corresponding inner clutch toothing7, 8.

Arranged in the axial interspace between the gear wheel 12 and theselector sleeve carrier 13 is a synchronizer ring 46, which isconcentric with the center line 14—14, is fixed with the ability forlimited rotation relative to the selector sleeve carrier 13, and hasouter locking toothing 47 which is concentric with the center line 14—14and is traversed in the customary manner by the clutch toothing 7, 8 ofthe selector sleeve 10 once the gear wheel and the shaft have beensynchronized.

In the illustrative embodiment in FIG. 2, the selector sleeve 10 hasclutch teeth 7 in accordance with the invention and conventional clutchteeth 8, arranged alternately in the circumferential direction. Each ofthe clutch teeth 8 has a central guide portion 16 with two guide faces21 and 22 of guiding length 43, which are symmetrical with respect to asignificant tooth longitudinal plane 33—33 containing the center line14—14. In the engaged position 48 of the selector sleeve 10, thisguiding length 43 is reduced to the shorter overlap length 50 relativeto the driver toothing 18, owing to the gear-change path 49 travelled.At their ends 25 and 26, the clutch teeth 8 have oblique end faces 27and 29 which slope relative to the longitudinal plane 33—33 of the teethand are symmetrical to the longitudinal plane 33—33 of the teeth, withthe result that their common vertex edge 31 lies in the longitudinalplane 33—33 of the teeth. An undercut tooth-flank portion 34, 35 startsfrom each of the two oblique end faces 27 and 29, in each case in thedirection of the center line 14—14 towards the guide portion 16, thesetooth-flank portions converging with straight flank lines in thedirection of the guide portion 16.

By virtue of a corresponding configuration of the clutch tooth 45 on theclutch ring 44 of the gear wheel 12, there is an axial engagementoverlap 51 between the clutch teeth 8 and 45 in the engaged position 48of the selector sleeve 10. The purpose of this overlap is to secure theselector sleeve 10 against jumping out in the engaged state by way of anundercut subjected to torque. Depending on the gear position andconstruction of the gearbox, a certain minimum overlapped length isnecessary here. This engagement overlap 51, which is “conical” by virtueof the convergence of the undercut flank portions 34, 35, isadvantageously short in the directions of the center line 14—14, thusallowing the overall length 52 of the gear wheel clutch 11, generallydesigned as a changing clutch for the gear wheel 12 and a second gearwheel 53, to be kept short. However, it is not possible reliably toprevent sticking of the selector sleeve 10 in the driver toothing 18 dueto the shortening of the guiding length 43 to the overlapping length 50.

This sticking is avoided by the invention by virtue of the fact that oneach of the clutch teeth 7, which are identical in their configurationwith the clutch teeth 8 in the initial state, one flank side 20* is setback by a constant amount 40 parallel to the significant longitudinalplane 33—33 of the teeth. This gives rise, at the transition between oneoblique end face 28 and the undercut tooth flank portion 35* in theregion of one end 25 of the clutch tooth 7, to an additional third guideface 36 with a flank line which is parallel to the center line 14—14 andis at a distance 37 from the significant longitudinal plane 33—33 of theteeth which is equal to the distance 38 of the guide face 20 set back inthis way on the central guide portion 15 of the clutch tooth 7. Anassociated adjacent driver tooth 41 on the selector sleeve carrier 13 iswidened in a corresponding manner, and there is thus no change in thebacklash.

The amount 40 can be chosen so that there is no longer an undercutresidual tooth flank portion (35*) Instead, an enlarged overall guideface extending continuously from the guide portion 15 to the oblique endface 28 is formed. That flank side of the clutch tooth 7 which lies onthe other side of the longitudinal plane 33—33 of the tooth is naturallyof conventional design; in the direction of the center line 14—14towards the guide portion 15, the oblique end face 27 which has a commonvertex 31 with the oblique end face 28, the vertex lying in thelongitudinal plane 33—33 of the tooth, merges into an undercut toothflank portion 35 which extends as far as the guide face 19 of the guideportion 15 and converges towards the longitudinal plane 33—33 of thetooth. The guide face 19 is at a distance 39 from the longitudinal plane33—33 of the tooth which is greater by the amount 40 than the distance38. In corresponding fashion, the driver tooth 42 of the selector sleevecarrier 13 which engages between the guide flank 19 and a conventionalclutch tooth 8 has the normal original tooth thickness.

In some or half of the clutch teeth 7 according to the invention, thetooth flank side having the guide face 19 can be set back by a constantamount instead of the tooth flank side having the guide face 20*. Twoclutch teeth 7, on one of which the guide face 19 and on the other ofwhich the guide face 20 or 20* is set back, can be arranged on bothsides of a conventional clutch tooth 8, or in front of and behind it inthe circumferential direction.

All these configurations in accordance with the invention have thecommon advantage that the overlap length 50 of a conventional clutchtooth 8, which amounts to less than half the length of a driver tooth 41or 42, is increased to an overlap length 54 which amounts to more thanhalf the length of a driver tooth 41 or 42, with the result that thesticking phenomena explained no longer occur.

In the imaginary example of a clutch tooth 9 for a selector sleeve inaccordance with FIG. 6, oblique end faces 30, 30 with a common vertexedge 31 lying in a longitudinal centre plane 33—33 of the tooth areformed on one end 25, symmetrically to the longitudinal center plane ofthe tooth. These oblique faces merge into respective guide faces 58 and59 extending parallel to the center line 14—14. The central guideportion 17 of the clutch tooth 9 has the customary symmetrical guidefaces 23 and 24 which, in the direction of the center line 14—14 towardsthe end 25, merge into respective tooth flank portions 55 and 56 whichare undercut relative to the guide faces 58 and 59, respectively, on thesame side and the flank lines of which likewise run parallel to thecentre line 14—14. If the selector sleeve is moved into its coupledposition 48 in this example and 51 represents the minimum amount ofengagement overlap, then the gear-change travel required for this isgreater by the length 57 of the guide faces 58 and 59.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Since modifications of thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

What is claimed is:
 1. Clutch tooth of a selector sleeve of a gear wheelclutch for coupling a gear wheel to its shaft, comprising: a guideportion, which is arranged centrally in relation to directions of acenter line of the selector sleeve, guide faces by which the clutchtooth is bounded in both peripheral directions of the center line, saidguide faces extending parallel to the center line, wherein the guideportion can be introduced so as to be axially displaceable and fixed interms of rotation into driver toothing concentric with and fixed interms of movement relative to the shaft, and ends forming a boundary inthe directions of the center line, each of said ends having two obliqueend faces, which are arranged in a roof shape relative to one anotherand which define a common vertex edge which lies in a significantlongitudinal plane of the tooth containing the center line, wherein eachof the side flanks comprises one of said guide faces of the guideportion, a tooth flank portion which adjoins it in the direction of thecenter line towards one end and is at a reduced distance from asignificant longitudinal plane of the tooth, wherein each of the obliqueend faces and one of the guide faces lie on the same side of thesignificant longitudinal plane of the tooth, wherein one oblique endface merges directly into an undercut tooth flank portion which, in thedirection of the guide portion, converges with straight flank linesrelative to the significant longitudinal plane of the tooth, wherein theother oblique end face merges, in the direction of the center linetowards the guide portion, into an undercut tooth flank portion whichconverges with straight flank lines relative to the significantlongitudinal plane of the tooth in the direction of the guide portion,the other oblique end face merging into the tooth flank portion via athird guide face which extends parallel to the center line and is at thesame distance from the significant longitudinal plane of the tooth asone of said guide faces of the guide portion which lies on the same sideof the significant longitudinal plane of the tooth, and wherein thedistance between the third guide face and the significant longitudinalplane of the tooth is less than the distance between one of said guidefaces of the guide portion which lies on the other side of thesignificant longitudinal plane of the tooth and the significantlongitudinal plane of the tooth.
 2. Selector sleeve of a gear wheelclutch for coupling a gear wheel to its shaft with at least one group offirst clutch teeth with guide faces formed exclusively on the guideportion and with at least one group of second clutch teeth, each clutchtooth of the second clutch teeth comprising: a guide portion, which isarranged centrally in relation to directions of a center line of theselector sleeve, guide faces by which the clutch tooth is bounded inboth peripheral directions of the center line, said guide facesextending parallel to the center line, wherein the guide portion can beintroduced so as to be axially displaceable and fixed in terms ofrotation into driver toothing concentric with and fixed in terms ofmovement relative to the shaft, and ends forming a boundary in thedirections of the center line, each of said ends having two oblique endfaces which are arranged in a roof shape relative to one another andwhich define a common vertex edge which lies in a significantlongitudinal plane of the tooth containing the center line, wherein eachof the side flanks comprises one of said guide faces of the guideportion, a tooth flank portion which adjoins it in the direction of thecenter line towards one end and is at a reduced distance from asignificant longitudinal plane of the tooth, wherein each of the obliqueend faces and one of the guide faces lie on the same side of thesignificant longitudinal plane of the tooth, wherein one oblique endface merges directly into an undercut tooth flank portion which, in thedirection of the guide portion, converges with straight flank linesrelative to the significant longitudinal plane of the tooth, wherein theother oblique end face merges, in the direction of the center linetowards the guide portion, into an undercut tooth flank portion whichconverges with straight flank lines relative to the significantlongitudinal plane of the tooth in the direction of the guide portion,the other oblique end face merging into the tooth flank portion via athird guide face which extends parallel to the center line and is at thesame distance from the significant longitudinal plane of the tooth asone of said guide faces of the guide portion which lies on the same sideof the significant longitudinal plane of the tooth, and wherein thedistance between the third guide face and the significant longitudinalplane of the tooth is less than the distance between one of said guidefaces of the guide portion which lies on the other side of thesignificant longitudinal plane of the tooth and the significantlongitudinal plane of the tooth.
 3. Gear wheel clutch for coupling agear wheel to its shaft with a selector sleeve according to claim 2,wherein two of said clutch teeth in said group of second clutch teethwhich are adjacent in the circumferential direction and have third guidefaces acting in opposite circumferential directions are arranged on bothsides of and symmetrically to a driver tooth which is fixed in terms ofmotion relative to the shaft and is widened in both circumferentialdirections by the respective difference in spacing of the third guideface of the adjoining clutch tooth.